Antimony and bismuth oxide cluster ions

The formation of charged antimony and bismuth oxide clusters in a pulsed ar c cluster ion source (PACIS) has been studied with time-of-flight mass spec trometric techniques. We compare series of antimony and bismuth oxide clust er anions with their known cationic counterparts. The anionic series (M2O3) (n)MO2- and (M2O3)(n)O-2(-) have been predicted proceeding from the known c ationic series (M2O3)(n)MO+ and (M2O3)(n)O+ by adding O2- and have been exp erimentally established. All these series contain the metal atoms (M=Sb or Bi) in the formal oxidation state +3. However, only in the case of antimony , oxygen rich oxide clusters appear, that can be explained with a gradual t ransition in the oxidation number from +3 to +5 of single antimony atoms in the cluster. To estimate the influence of the special oxide formation cond itions comparative investigations with the PACIS and a laser vaporisation c luster source have been carried out for bismuth oxide cations. The similar oxide cluster distributions at comparable oxygen availability display clear ly that the special thermodynamical stability of the discussed magic cluste rs is the significant driving force for their formation.